1. Field of the Invention
The present general inventive concept relates to a hard disk drive (HDD), to retracting a head, and more particularly, to a retract control method of an HDD to prevent a head from landing on a disk due to a retract failure and an HDD using the same.
2. Description of the Related Art
An HDD is a recording device used to store information. The information is typically recorded on concentric tracks formed across a surface of a magnetic disk. The disk is mounted to a spindle motor, and the information is accessed by a head mounted to an actuator arm rotated by a voice coil motor (VCM). The VCM rotates an actuator by a VCM driving current, moving the head across the disk.
The head reads the information recorded on the surface of the disk by sensing a variation of a magnetic field formed on the surface of the disk. To record data on the disk, a write current is supplied to the head, generating a magnetic field from the head. The data is recorded on the disk by magnetizing the surface of the disk using the generated magnetic field.
In the HDD, an operation of retracting the head on a ramp-(hereinafter known as a “retract operation”) is performed when power saving is required or when it is necessary to protect the head and the disk from shock from an outside of the HDD, such as when an idle state is maintained, when the shock from the outside of the HDD is sensed, when a free-fall state is detected, when an operation of the HDD is finished, or when driving power of the HDD is suddenly cut off.
FIG. 1 is a schematic plan view illustrating an HDD 100 using a ramp structure.
Referring to FIG. 1, the HDD 100 includes at least one disk 12 rotated by a spindle motor 14. The HDD 100 also includes at least one head 16 adjacently located to a surface of the at least one disk 12.
The head 16 can read or write information from or on the rotating disk 12 by sensing a magnetic field formed in magnetic regions 34 on the surface of the disk 12 or magnetizing the magnetic regions 34 on the surface of the disk 12. Though a single head 16 is shown in FIG. 1, the head 16 includes a write head for magnetizing the disk 12 and a separated read head for sensing the magnetic field of the disk 12.
The head 16 can be assembled on a slider (not shown). The slider is formed in such a structure to generate an air bearing between the head 16 and the surface of the disk 12. The slider is combined with a suspension 20. The suspension 20 is combined with a head stack assembly (HSA) 22. The HSA 22 is attached to an actuator arm 24 having a voice coil 26. The voice coil 26 is located adjacently to a magnetic assembly 28 specifying (supporting) a voice coil motor (VCM) 30 together with the voice coil 26. A current supplied to the voice coil 26 generates a torque which rotates the actuator arm 24 around a bearing assembly 32. The rotation of the actuator arm 24 moves the head 16 across the surface of the disk 12.
When the HDD 100 illustrated in FIG. 1 performs a retract operation, the head 16 is laid on a ramp 6 illustrated in FIG. 2, which is installed in the side of the outer circumference of the disk 12.
FIG. 2 schematically illustrates the retract operation using the ramp 6. Referring to FIGS. 1 and 2, when the retract operation commences, the head 16 retracts (unloads) onto the ramp 6 from the disk 12.
FIG. 3 is a cross-sectional view illustrating the ramp 6 of FIG. 2. The ramp 6 has a cross section of a ladder shape and includes a first incline 6d, a flat surface 6c, a second incline 6b, and a safety zone 6a. Referring to FIGS. 1-3, when the retract operation is performed, the head 16 rises along the first incline 6d, and lands in the safety zone 6a. In reality, a projection 20aprojected under the slider 20 contacts the ramp 6.
When the retract operation fails, i.e., if the head 6 cannot rise over the first incline 6d of the ramp 6, the head 16 lands on the disk 12, and thus the head 16 and the disk 12 may be damaged. In particular, in a small-sized HDD used for a mobile device, if the head 16 lands on the disk 12, the HDD cannot be used any more in most cases due to the sticking between the head 16 and the disk 12.
Thus, a retract control method for guaranteeing a trustworthy retract operation is required.